The air pollutants exist in two major physical phases: particle phase pollutants and gaseous phase pollutants. The particle phase pollutants are pollutants with significant physical sizes including dust particles, airborne bacteria and mold. They may be composed and be bound together by different matters with different compositions. The gaseous phase pollutants are pollutants with simple chemical structures. The size of the gaseous phase pollutants are small from angstrom to nano-scale.
There are many methods to eliminate the particle phase pollutants or pollutants with significant physical sizes. Conventionally, a High-Efficiency Particulate Arresting filter (HEPA filter) is used to filtrate particulate matter from the polluted air. On another hand, some may utilize a high-voltage to produce an electrostatic effect for dust removal. Some may release negative ion to the ambient, which eventually charges up the dust particulate, and allows them be collected in some regions which are relatively neutral or positively charged.
The efficiency and performance of using HEPA filter for dust removal is always better than that of the dust removal by the ionization or by the electrostatic precipitation methods. Nevertheless, the HEPA filter is a consumable item and cannot be recycled. It induces a high airflow resistant when the air is passing through it. When an air purifier integrated with HEPA filter, a fan with motor of relative large torque is usually needed in order to compensate the high airflow resistant that induced. It is not a environmental friendly method as more energy need to be consumed.
The air resistance induced by the electrostatic dust removal or particulate precipitation methods with the high-voltage component is usually low. To further improve the performance and efficiency of dust removal by a high-voltage component, higher operation voltage is usually employed. Though the operation current of the high-voltage is usually low, increasing of the operation voltage of the high-voltage component will lead to a high power consumption, which is not environmental friendly. In the past, many inventions disclosed special circuit design for the purpose to improve the performance of the high-voltage component for the electrostatic precipitation. Increase the operation voltage of the high-voltage component or decrease the distance between the positive and negative components of the electrostatic precipitator can generally help to improve the performance and efficiency of the dust removal. However, harmful ozone may be released as a side-product by these methods. On another hand, more strict regulations and requirements are imposed on the air purifier where high-voltage electrostatic precipitator for the safety concerns, which as a result, lower the flexibility and freedom on the design for the air purifier or air purification system. It is therefore difficult for designer of air purifier product to made the volume of air purifier small and compact.
Chinese utility model ZL200820120906.7 discloses an air purifier with high-voltage electrostatic precipitation component, where needle-shape charger is passing through the cylindrical electrostatic hollow collectors is disclosed. The invention reveals a one dimension, unidirectional and forwarding airflow path design. In order to increase the efficiency, very long cylindrical electrostatic hollow collectors are needed. Nevertheless, when the long cylindrical electrostatic hollow collectors occupied fully with dirty dust and particulates after used, the user would find the maintenance works become very annoyed and not convenience. The need of long cylindrical electrostatic hollow collectors would also lower the flexibility on air purifier design.
French patent FR 2623424 (A1) discloses that downstream of an ionization mean, a metal device for trapping the ionized particles by an electrostatic effect is installed. The metal device is curvature in shape and it is in perpendicular with the direction of the airflow. The airflow paths are allowed to be changed within a 2 dimensional planar orientation when come across the metal device, and hence the dust removal efficiency is therefore improved. Nevertheless, the process of fabrication of the metal device into this particular curvature shape during manufacturing is costly and complicated. Same as the mentioned Chinese utility model (Utility Patent No.: ZL200820120906.7), the maintenances works by the user after used are inconvenience as there are too many hidden curvature surface within the dust collector.